Does a delay introduced by the PWM converter depend on the modulation scheme used (unipolar vs. bipolar, continuous vs. discontinuous)? No.
The only reason for this delay is that the modulator fed by the sampled control signal has to use ZOH (zero-order hold) in order to compare this signal with the triangular carrier signal. The delay related to ZOH is equal to T/2. A digital controller introduces a delay of T. Therefore, if no other significant delays are present in the measurement/acquisition/conditioning/filtering interface, the delay of 1.5*T should be used to calculate current controller gains. The example demonstrates such a procedure.